I really enjoy these kinds of game. This reminds me a lot of Penguin Learns to Fly. A couple of suggestions:
* make the mushrooms spring the player, regardless of their y velocity. The mushrooms don't detect the player and you hit the ground and reset.
* after the player hits the ground, allow the player to bounce along the ground and only reset after coming to a complete stop.
* the coins should be scattered throughout the level, not just at the beginning. This means the player could use a Flap to try and collect the coin